The present invention is situated in the field of protection of electronic modules.
It applies especially but without limitation to the protection of a microcircuit card, for example one complying with the ISO 7816 standard.
Within the scope of microcircuit card protection against fault injection attacks, a known countermeasure consists of writing a predetermined value into a reserved area of a nonvolatile memory of the card when a disruption is detected, the content of this area being checked by the card at the beginning of each command; when this content is equal to the aforementioned predetermined value, the card refuses to execute the command and the card becomes unusable.
In known fashion, a write operation into nonvolatile memory is compulsorily preceded by the charging of a charge pump, which involves a very noticeable increase in the current consumption of the card.
This sudden variation can be observed by simple power analysis (SPA) using a resistor in series with the card.
It is therefore possible, for an attacker having a charge pump charging detection module available, to bypass the countermeasure described earlier by immediately cutting off the power supply of the card to prevent the writing of the predetermined value into the area, when it detects a rise in power consumption that is not usual in normal operation and therefore representative of the fact that the card is trying to make itself inoperable.
The invention offers a solution to this problem.